Don’t feed my sister

Our third daughter loves to pretend to be a puppy. Here she is, rolling about like a dog:

Today, I was getting some chocolate milk ready for the girls for a special treat. My daughter was yipping and crawling about. I asked her if puppies like chocolate milk. She said yes, but my oldest daughter, ever intelligent and vigilant, quickly informed me that chocolate milk was not at all a good thing to give puppies.

I laughed and gave them all their milk. My oldest daughter started to draw while drinking hers. A few minutes later, she brought me a picture of a dog with a line drawn through it. When I asked her about it, this is what she told me: